Vibrationless percussive tools



Jan. 3, 1967 c. LEAVELL VIBRATIONLESS PERCUSSIVE TOOLS 2 Sheets-Sheet l Filed sept. 16. 1965 Jan. 3, 1967 c. LEAVELL.

VIBRATIONLESS PERCUSSIVE TOOLS Filed Sept. 16, 1965 2 Sheets-Sheet 2 'O2 FIGA' United States Patent O 3,295,614 VIBRATIONLESS PERCUSSIVE 'IOQLS Charles Leavell, 206 S. Fairfield Ave., Lombard, Iii. 60148 Filed Sept. 16, 1965, Ser. No. 490,162 27 Claims. (Cl. 173-439) This application is a continuation-in-part of my copending patent application, Serial No. 240,288, tiled November 27, 1962, now abandoned.

This invention relates generally to tripartite vibratile structures comprising (l) a first desirably or unavoidably vibratin g body, (2) a second body in which the occurrence of vibration is objectionable, and (3) connecting structure or linkage means for accomplishing a necessary transmitsion of force between such two bodies; and it relates more particularly to the problem of preventing the transmission of vibration Athrough such connecting structure from the first vibratory body to the second body in which the occurrence of vibration is objectionable. In an environmental sense, the invention is concerned with vibrationless percussive tools of the type disclosed in my issued patents, No. 3,028,840 and No. 3,028,841.

In Patent No. 3,028,841, I disclosed an inventive concept of fundamental character generally applicable to an exceedingly wide variety of tripartite vibratile structures for substantially eliminating the transmission of vibration between such first and second bodies thereof while maintaining a necessary transmission of force therebetween; and I exemplified such invention in the environment of percussive tools because the problems encountered in eliminatingl vibration in tools of this class are more diiiicult of solution than those encountered in most other environments. The paving breaker was selected for specific consideration because it typifies percussive tools generally and presents, perhaps, the most numerous and difiicult `problems requiring solution in the realization of a vibrationless percussive tool.

As explained in such prior patent, the usual paving breaker includes a casing defining an axially extending cylinder having a hammer or piston reciprocable therein, and a steel spike or work member slidably carried by the casing for limited axial movements with respect thereto. Such spike is adapted to receive impact force from the hammer (usually through an anvil or tappet interposed therebetween) at one end of the reciprocatory stroke thereof, and the hammer is reciprocated within its cylinder by the alternate application of pressure liuid (usually compressed air) to the opposite ends or faces thereof. The `impact force transmitted from `the hammer to the spike is delivered thereby to a concrete slab or other work material to break or demolish the same.

In such usual paving breaker, the charges of compressed air alternately admitted into the opposite ends of the `cylinder to respectively reciprocate the hammer in directions toward and away from the spike are each reactively applied against transverse surfaces defining the end closures of the cylinder, and as a consequence of such reactive application of pressure force to the cylinder end closures, the casing is alternately moved in opposite directions or is vibrated along the axis of reciprocation of the hammer. In many tool structures, the hammer is reciprocated at a frequency that may approximate 1,200 cycles each minute; and, therefore, the pressure forces (often in the order of 500 pounds) reacting alternately against the opposite ends of the casing cylinder introduce an exceedingly violent and objectionable vibration into the casing.

It is evident from the foregoing description that the usual paving breaker is a tripartite vibratile structure in which the compressed air pressure forces applied to the opposite ends of the hammer and which react alternatelv lll ice

against the opposite end closures of the casing cylinder define the aforementioned connecting structure or linkage means accomplishing a necessary transmission of force between the hammer, which is a desirably or unavoidably vibrating body, and the casing, which is a body in which the occurrence of vibration is objectionable.

The apparatus disclosed in such prior Patent No. 3,028,- 841 for eliminating the vibration ordinarily `introduced into the casing of a percussive tool by the pressure forces reactively applied against the ends of the casing cylinder in energizing the reciprocatory cycle of the hammer includes means for counterbalancing such alternately developed reactive pressure forces by the respective simultaneous application therewith to the casing of pressure forces substantially equal in value to and oriented in opposition to the hammerenergizing pressure forces. Such pressure-force counterbalancing means comprises a hermetic barrier that, in the specific structure, takes the form of an oscillator or oscillatory mass member reciprocable within a separate cylinder therefor.

The oscillatory mass member in certain situations because of random and irregular recoil forces fed into the tool structure through the steel spike as a consequence of the non-homogeneity of the slab being penetrated thereby unpredictably exhibits a tendency to migrate toward one end of its cylinder and impact the endl closure thereat, which condition of impact is undesirable in that it would reintroduce vibration into `the casing. The invention disclosed in such prior patent is also concerned with avoiding the impact-generating configuration of the oscillator with the end of its cylinder, and such avoidance is accomplished by stabilizing the mean position of the oscillator in a condition of impact-preventing intermediacy through the provision of an automatic control system that includes a pneumatic column operative to bias the oscillator structure in a direction away from impact with such one end of its cylinder.

This pneumatic column defines a forcetransmitting linkage or connecting structure coupling the necessarily vibrating oscillator and the cylinder therefor, which cylinder constitutes the body in which the occurrence of vibration is objectionable. Such automatic control system provides first, an arrangement for maintaining the force transmitted by such pneumatic column relatively constant dur ing any one cycle of recpirocation of the oscillator, and second, feedback control means for regulatively adjusting the value of such relatively constant force over a plurality of reciprocations of the oscillator to positionally stabilize the same and thereby maintain it in a condition of impact-preventing intermediacy relative to the ends -of its cylinder.

In Patent No. 3,028,841, a single oscillatory mass member, reciprocable in its own cylinder, is comprised by the pressure-force counterbalancing system, and the axis of reciprocation of the mass member is angularly oset from the axis of reciprocation of the blow-striking hammer ofthe paving breaker. Such offset gives rise to the use of a special orientation for the two axes, which special orientation is identified as a condition of copivotality (see such patent for an explanation thereof). In Patent No. 3,028,840, the need for or desirability of using such special orientation of the two axes is obviated by dividing the single or unitary Ioscillatory mass member into two separate but substantially identical oscillator components, each with its own related force counterbalancing and automatic control systems, and disposing the two oscillator components symmetrically with respect to the hammer `and its axis of reciprocation. Reference may be made to such Patent No. 3,028,840 for a detailed description of the symmetrical relationship of the oscillator components and blow-striking hammer and of the force counterbalancing and automatic control systems of such twin oscillator tool.

vThe present invention is concerned with vibrationless percussive tools `of the character disclosed in the aforementioned patents and departs from the teachings thereof in a number of particulars such as the placement, orientation, and certain functional interrelationships of the oscillatory mass member with both the hammer of the tool and casing thereof. Further departures from such .prior disclosures concern the manner in which the return stroke of the blow-striking hammer is energized; the manner in which the oscillatory mass member is maintained in a predetermined mean position of impact-preventing separation with cylinder surfaces cooperatively arranged therewith; the structural arrangement of the steel spikeand-tappet composition, the positioning thereof with respect to the tool casing, Iand the provision of means for automatically maintaining such composition in a predetermined relation with respect to the tool casing; the manner in which the feeding force, usually manually applied, is delivered through .the tool casing to internal components therewithin; and the manner in which the tool structure is longitudinally integrated. Additional features of departure as well as a number of advantages and objects of the invention will become apparent as the speciii-cation develops.

'Embodiments of the invention are illustrated in the accompanying drawings, in which FIGURE 1 is a longitudinal sectional view of a percussive tool embodying the invention, the section being taken generally along the lon-gitudinal axis of the tool;

FIGURE 2 is a broken side View in elevation of such tool but with the motor means for energizing the rotary valve being electric rather than pneumatic;

FIGURE 3 is a transverse sectional view taken generally yalong t-he plane 3 3 of FIGURE 1; and

FIGURE 4 is an enlarged, longitudinal sectional view of a pressure control device used in the tool structure.

The exemplary percussive tool illustrated in the d-rawings, is a pneumatically actuated paving breaker comprising a casing composition defined by an inner casing element 11 and an `outer shell or casing element 12 coaxially circumjacent thereto. The inner casing element 11 is an elongated tubular element having a hollow interior defining `an axially extending main cylinder 13. Positioned within the cylinder 13 lfor reciprocatory movement with respect thereto is a blow-striking hammer or pistons 14, and also reciprocable within such cylinder is an oscillator or oscillatory mass member 15. Thus, the hammer and oscillator are serially mounted for reciprocation in the same bore, namely the cylinder 13; and, therefore, the axes of reciprocation of the piston and oscillator are coincident, and with respect to these reciprocable components the tool may be said to be a mono-cylinder tool.

The central portion of the hammer 14 is of reduced diameter, and an annular channel 16 is deiined between such restricted central portion and the circumjacent cylinder wall of the inner casing element 11. The lower end portion 14a of the hammer slidingly and sealingly engages the wall of the cylinder 13, and for purposes of identification the lower face of t-he hammer is designated with the numeral 14a. The upper end portion 1413 of the lhammer slidingly engages the wall of the cylinder 13 and yis equipped with a plurality of langularly spaced and axially extending grooves 14e` that define flow passages connecting the annular chamber 16 with the cylinder space above the hammer. F-or identiiication, the upper face `of the hammer is denoted with the numeral 14h.

T'he oscillatory mass member 15 has an intermediate portion of reduced diameter, yand the member is equipped rat the opposite ends thereof with enlarged heads or piston portions a and 15b. The upper and lower faces of the oscillator are respectively designated with the numerals 15a' and 15b. Mounted 4in the inner casing element 11 within the cylinder 13 defined thereby is Va sleeve 17 coaxially circumjacent the restricted intermediate portion of the oscillator 15 and slidingly and sealingly engaged thereby. Such structural arrangement results in a pair of upper and lower control cylinders 18 and 19 formed between the oscillator 15 and surrounding wall of the inner casing element 11; land such control cylinders are pressure-isolated from each other by the sleeve 17 which, at its upper end, defines .the lower end closure 18a of the control cylinder 18 and, at its lower end, deiines the upper end closure 19a of the control cylinder 19.

The piston 15a has a downwardly-oriented piston surface 18]; disposed in facing relation with the cylinder end closure 18a and, similarly, the lower portion 15b has an upwardly-oriented piston surface 19b disposed in facing relation with the cylinder end closure 19a. Quite evidently, the respectively `facing surfaces 18a-18b and 19a- 1911 are relatively reciprocable in accordance with the reciprocatory displacements of the oscillator 15 and are pressurizable, -as are the respectively associated control cylinders 18 and 19.

A pair of aligned ports 18C respectively formed in the cylinder wall of the casing element 11 and in a collar or sleeve 20 coaxia'lly circumjacent the same form an inlet for the control cylinder 18, and such inlet communicates with a relatively large annular tank space or constant pressure space 18d formed between the collar 20 and outer casing element 12. The space 18d is axially terminated by outwardly extending annular flanges 21 and 22 provided by the collar 20 and which engage the inner surface of the casing element 12. A plurality of exhaust ports 18e formed in the inner casing element 11 are adapted to be traversed by the cylindrical surface of the piston 15a, and such exhaust ports communicate with atmosphere through an annular collection space 181, passage 18g and annular channel 18h, all of which are provided in the upper annular flange 22 Aof the sleeve 20, and a port 181' formed in the outer casing element 12.

The control cylinder 19 has a similar arrangement of components and, accordingly, has ,an inlet 18e communi- Ieating with a relatively large annular tank space or constant pressure space 19d axially terminated lby the annular liange 21 and a lower annular flange 23 provided by the sleeve 20, and the cylinder has an exhaust to atmosphere comprised by a plurality of exhaust ports 19e, collection space 19], passage 19g, annular channel 19h and port 191'.

The volumes of the tank spaces or constant pressure spaces 18d and 19d (respectively aggregated With the volumes of the associated cylinders 18 and 19 and the ports 18C and 19C) Iare sutiiciently large relative to any changes in such aggregate volumes caused by the reciprocatory displacements of the oscillator, and in particular of the piston portions 15a and 15b thereof, that substantially no change in pressure occurs within such spaces as the volumes thereof are cyclically increased and decreased in accordance with the reciprocatory displacements of the oscillator. Further, the inlets 18C and 19C have suiiiciently large cross sectional areas (a plurality of angularly spaced inlet ports may be used if desired) that no significant pressure gradients are established thereacross as the air reciprocates therethrough in accordance with the cyclic increases and decreases in the volumes of the control cylinders as the oscillator 15 reciprocates.

Any number of exhaust ports 18e and 19e may be provided, and it is desired that at least certain of such ports should be axially spaced, as shown in FIGURE l, for the purpose of attenuating or damping the corrective response of the automatic control system in its function of maintaining the range of the reciprocatory displacements of the oscillator 15 in the aforementioned predetermined position of intermediacy. This arrangement of exhaust ports is provided so that any tendency of the oscillator to be subject to a hunting action is minimized or obviated. For further elaboration of this type of exhaust system, reference may be made to my copending patent application, Serial No. 186,198, filed April 9, 1962, now Patent No. 3,200,893.

For assembly purposes, the oscillator in the specific structure illustrated is formed in two parts with the head or piston 15a being a separate component, as indicated by the dotted lines adjacent the upper end thereof, so that such head may be mounted upon the intermediate portion of the oscillator after the intermediate portion thereof is in position within the cylinder 13 (and sleeve 17); and such 'unification of the oscillator components may be accomplished in any conventional manner as, for example, by means of a press fit assembly. The sleeve 17 may be properly located and secured within the cylinder 13 in any conventional manner as, for example, by a press fit, with mounting pins, etc.

The hammer 14 has an axially extending bore or passage as does the oscillator 15, and such bores are axially aligned and slidingly and sealingly receive therein a hollow tube 24 equipped at its upper end with a laterally extending closure cap 25 that seats within -a recess 26 provided therefor in a cap or cover 27 equipped with internal threads which matingly engage the externally threaded upper end portion of the outer casing element 12. The inner lcasing element 11 is provided with an upper end closure 28 having a central opening 28a therein that passes the tube 24 therethrough. The closure 28 is held in position by the cap 27, and the perimetric edge portion of the closure about the opening 28a therethrough seats against the annular closure 25 of the tube 24. Thus, the tube is confined `by the cap 27 and closure 28 against substantial longitudinal displacements along the reciprocatory axis of the hammer 14 and oscillator 15. For convenience of identification, the -lower surface of the closure 28 is indicated with the numeral 28a'.

The hollow tube 24 defines a How passage therethrough that interconnects the lower end portion 29 of the cylinder 13 with the upper end portion 30 thereof, and to effect such interconnection the tube is open at its lower end and is provided with one or more openings 31 adjacent its upper end. A relatively large tank space or constant pressure space 32 is in open communication with the upper cylinder portion through a plurality of relatively large openings 33 formed in the inner casing element 11, and such const-ant pressure space is defined between the inner and outer casing ele-ments and is limited or terminated in axial directions by the annular flange 22 of the sleeve 20 and by the cap 27. In a similar manner, the cylinder vspace 29 communicates directly with a relatively large tank space or constant pressure space 34 through a plurality of openings 35 formed in the cylindrical wall of the casing 11, and such constant pressure space is defined between the inner and outer casing elements and is limited or terminated in one axial direction by a ring 36 disposed between Ithe inner and outer casing elements, and in the other axial direction by an annular flange 37 provided by a cylinder block 38 mounted within the outer casing element 12 so as to form the lower end closure of the cylinder 13.

The aggregate cross sectional areas of the respective groups of openings 33 and 35 are such that substantially no pressure gradients occur in the air flowing therethrough as the hammer and oscillator components reciprocate. Additionally, the volumes of the respective constant pressure spaces 32 and 34, aggregated with the volumes of the respectively associated cylinder spaces 30 and 29, are sufficiently large relative to any changes in such aggregate volumes caused by the reciprocatory displ-acements of the hammer 14 and oscillator 15 that substantially no change in pressure occurs therein as a consequence of such displacements. However, the mainrtenance of substantially constant pressures above the oscillator and below the hammer and the volumetric relationships through which such pressures are realized are not critically 4necessary in the tool structure being considered because the volumes comprising the spaces 30-32 and 29-34 are in open communication through the tube 24 and thereby simultaneously pressurized, and because the areas of the downwardly-facing upper end closure of the space 30-32 and upwardly-facing lower end closure of the space 29-34 (and other spaces in communication therewith, as will be described later) are substantially equal. Similarly, the upwardly-facing lower end cl-osure of the spa-ce 30-32 and downwardly facing upper end closure of the space 29-34 have substantially equal areas. Therefore, the pressure forces in such spaces 30-32 and 29-34 which are reactively applied to the casing counterbalance each other in their reactive applica- Ition to the casing, and even if variable in magnitude, would not introduce vibration into the casing.

The cylinder block 38 is provided centrally with an opening 38a aligned with the reciprocatory axis of the hammer and oscillator, and slidingly and sealingly eX- tending through such opening is the upper stem portion 39 of an anvil-like upper end 40 of a work member 41. In the usual paving breaker structure, the steel spike or work member has impact forces transmitted thereto from the reciprocable hammer through the intermediate agency of a separate anvil or tappet member which is used for the primary purpose of sealingly closing the lower end portion of the hammer cylinder to thereby protect the interior thereof from dust and dirt. The need Ifor such anvil component arises from the requirement for frequent replacement of the work members which, in conventional tool structures, dull quite rapidly. As a consequence of such need `for frequent replacement, it would be uneconomical to contour the upper end portions of such work members and machine the same to the close tolerances necessary to provide an effective dust seal; and in addition, such work members would make the interchange or replacement thereof slow and tedious. In the specific tool being considered herein, the work member 41 and anvil-like upper end portion 40 thereof (sometimes hereinafter referred to for convenience as member) are unitary or integral components, for it is intended that the work member be a permanent part of the tool; that is to say, a part that does not require frequent replacement. A permanent-type spike, the characteristics thereof, and other pertinent information relative thereto are set forth in my copending patent application, Serial No. 208,436, led July 9, 1962.

As is evident in FIGURE 1, the cylinder block 38 provides an upwardly facing surface 38a' extending inwardly from the cylindrical casing element 11 at the lower end thereof and into adjacency with the upper end portion or stem 39 of the member 40. The upwardly-facing surface 39a of the stem 39 is normally located within the cylinder end portion 29 above the closure surface 38a thereof so as to receive blows from the hammer 14. The member 40 below the upper end portion 39 thereof is enlarged in diameter and forms a piston, separated into upper and lower sections 40a and 40h by a laterally extending annular piston flange 40C located at substantially the mid-portion thereof.

An upper control sylinder 42 defined by the cylinder block 38 slidingly and sealingly receives the piston 40a therein, and the control cylinder 42 has a downwardly oriented upper end closure 42a facing an upwardly oriented surface 42b on the piston section 40a. An inlet opening 42e` formed in the cylinder block 38 connects the cylinder 42 with a relatively large tank space or constant pressure space 42d; and the cylinder is provided with an exhaust system formed by a plurality of exhaust ports 42e which open into a passage 42)C that communicates through an anvil-compensating 4cylinder space 43 and a lateral extension 42g with an annular collection chamber 42h exhausting to atmosphere through a port 421' formed in the outer casing element 12. As seen in FIGURE 1, since the passages 42]c and 42g communicate with each other through the cylinder space 43, such cylinder space 43 and passage 42j are necessarily maintained at atmospheric pressure through the passage 42g.

The annular flange 40e of the member 40 is located within the cylinder space 43 and slidingly and sealingly engages the walls thereof. Such cylinder space at its lower end has an upwardly oriented surface 43a which faces a downwardly oriented surface 40a' provided by the piston or flange element 40C. The element 46c also has an upwardly oriented surface 4Gb facing the downwardly oriented upper end closure 43h of the cylinder 43. The lower end portion 29 of the main cylinder 13 is connected with the lower end portion of the -anvilcompensating cylinder 43 by a plurality of flow passages 44, 45 and `46 formed in the member 40, and suc'h passages extend lbetween the face 39a and surface 40a' of such member. Consequently, the cylinder space 29 and that portion of the cylinder 43 which is defined between the facing surfaces 40a' and 43a are simultaneously pressurized and, therefore, are continuously maintained at substantially the same pressures.

The surface 43a is provided by a plug 47 having a centrally disposed cylindrical portion extending into the lower end of the cylinder 43, and having also a laterally extending lower end portion that seats against the bottom edge of the cylinder block 38. As seen in FIGURE l, the lower end of the outer casing element 12 is turned inwardly and lies below the plug 47 and in abutment therewith so as to maintain the same in llrm engagement with the cylinder block 38.

The plug 47 denes therein a lower control cylinder 48 having an upwardly oriented, lower end closure 48a facing a downwardly oriented piston surface 48b provided yby the piston 40h. An inlet opening 48C connects the cylinder 48 with a relatively large tank space or constant pressure space 48d provided by the cylinder block 38 at the lower end thereof, and the cylinder 48 is exhausted to atmosphere through a plurality lof outlet openings 48e that open into an annular collection space 431 connected by a channel 48g to the aforementioned annulus 42h and exhaust port 421'.

As shown more clearly in FIGURE 3, a plurality of exhaust ports 421' are provided by the outer casing element 12 in angularly spaced relation thereabout, and each such port communicates with the annular channel 42h. Also, the constant pressure space `48a! is seen to comprise a plurality of angularly spaced, axially extending chambers respectively separated by a plurality of similarly oriented, radially extending ns 49 provided by the cylinder block 38 for the purpose of strengthening the same. Such individual chambers comprising the constant pressure space 48d are lall interconnected at their lower ends by a continuous annular channel 50 (see FIGURE l) in communication therewith which is formed in the plug 47. The aforementioned exhaust passage 42g is formed through one such fin, as is the passage 48g.

The illustrated paving breaker structure is a pneumatically actuated tool, and is adapted to be connected to a suitable source (not shown) of compressed air or other gaseous fluid through a coupling 51 removably secured to -an outwardly extending boss 52 provided by the outer casing element 12. An inlet passage 53 extends inwardly through such boss, and at one end communicates with the connector Sil and at its other end opens into an annular chamber 54 formed in the sleeve which, as heretofore explained, is interposed between the inner and outer casing elements. The chamber 54 is axially terminated by the aforementioned annular flange 23 and by an annular flange 55 spaced axially therefrom.

At one location therealong, the flanges 55 has a relatively large port or inlet opening 56 formed therein, and such opening is provided with a valve seat along the upper edge thereof adapted to be engaged by a control valve 57 equipped with an elongated stem 58 extending upwardly through bores provided therefor in the flanges 23,

21 and 22 (a bushing 'may be located in the latter flange, as shown, to further guide the valve stem) of the sleeve element 2t). The valve is biased into the closed position thereof, shown in FIGURE l, by a helical spring 59 that seats at one end -against the undersurface of the flange 2l and at its other end upon a washer or seat element 6l) lsecured in the position shown along the stem by a pin or other conventional means.

At its upper end, the valve stem 52 is equipped with a laterally extending flange or cam follower 6l adapted to be engaged by a cam 62 carried at the end of a rotatable lever or rod 63 mounted within a passage or bore provided therefor in one of the handles T, which handles are formed integrally with or are otherwise rigidly related to the outer casing element 12. The rod 63 is resiliently biased into the angular position illustrated, in which the valve 57 is closed, by a spring 64 effective to supplement the biasing force of the helical spring 59. The spring 64 is a conventional torsion-type spring operative to resiliently resist rotation of the rod 63 in a direction that opens the valve 57.

The rod 63 may be selectively rotated against the biasing force of the springs 64 and 59 to elevate the stem 58 and valve 57 by a trigger or valve-control lever 65 pivotally supported adjacent one end .by the outer casing element l2 and provided at its opposite end with a bifurcated portion that engages a pin 66 carried by the rod 63. When the lever is depressed, the rod 63 is rotated in a counterclockwise direction, as viewed from the right in FIGURE 1, and the cam 62 drives the cam follower upwardly, whereupon the valve rod 58 will be elevated to lift the Valve 57 from its seat and permit actuating fluid to flow through the opening 56 from the inlet passage 53.

With the valve S7 open, pressure fluid llows downwardly through the port 56 and enters an annular chamber 67 provided by the sleeve 26 and circumjacent outer casing element 12. The pressure fluid ows outwardly from such chamber through a port or passage 68 provided in the lowermost flange of the sleeve Ztl. Such lower ange is axially spaced from the ring 36, and supported within the space thus defined between the ilange and ring is a rotary valve 69 which is a ring-shaped element located coaxially circumjacent the inner casing element 1I. The valve 69 is rotatable with respect to the casing elements I1 and 12, and the upper and lower faces of the valve slidingly and seal-ingly engage the surfaces contiguous thereto, which surfaces are respectively provided by the lower flange of the sleeve 20 and by the ring element 36.

The rotary valve 69 is equipped along the circumferential surface thereof with teeth forming a ring gear '70 which meshes with a drive gear 70 (FIGURE 2) mounted upon a shaft 71 drivingly connected to a motor means 72 so as to be rotated thereby. As shown most clearly in FIGURE 2, the motor means comprises a pair of relatively sm-all motors 'i3 and 74, each of which is drivingly connected to the shaft 71 to simultaneously apply torque thereto in the same angular direction. Quite evidently, energization of the motor means rotates the shaft 7l, the drive gear 70 mounted thereon and, therefore, the rotary valve 69.

The valve 69 is provided with `one or more arcuate grooves or channels 75 formed along the upper surface thereof, and each such channel or groove provides an inlet passage adapted to register with the passage 68 for a predetermined period during each complete rotation `of the valve 69 so as to receive pressure fluid from such passage. During the same period of registration, the channel also registers with a port 7S formed in the wall of the inner casing 1l; and, therefore, during each period of registration pressure fluid flows from the inlet port 56, into the chamber 67, through the passage 68, through the channel 75 and port '75', and into the annular space 16 defined between the intermediate portion of the hammer 14 and circumjacent inner casing 1l.

The charge of pressure uid admitted to the annular chamber 16 flows upwardly therefrom through the recesses or grooves 14e in the upper end portion 1411 of the hammer, and into the cylinder space defined between the hammer and oscillator. Stich charge of pressure iluid acts downwardly upon the face 14b of the hammer to energize the reciprocatory cycle thereof and drive the hammer into impact engagement with the upper surface 39a' of the work member 41. The charge of pressure uid concurrently reacts upwardly against the downwardly oriented face 15b of the oscillator 15, and thereby tends to reciprocate the oscillator upwardly. The interval of communication of each channel 75 with the passage 68 `and port 75 depends up-on the arcuate length of the channel and the velocity of rotation of the rotary valve 69.

The rotary valve 69 is also provided with one or more arcuate grooves or channels 76 formed in the lower surface thereof, and each such groove is adapted to pe'- riodically communicate with the port 75 and with an exhaust system to atmosphere comprising a passage 77 through the ring 35 and a port 78 in the outer casing element 12. The exhaust channels 76 and inlet channels 75 are angularly located with respect to each other in spaced apart relation so as to alternately and successively register with the port 75 in such a manner that the cylinder space above the hammer 14 `and below the oscillator is pressurized to drive the hammer downwardly toward impact with the upper end of the work member 41 because of the charge of pressure fluid acting downwardly upon the upper hammer surface 1412', and subsequently the cylinder space above the hammer and below the oscillator is exhausted to atmosphere to enable the hammer to be reciprocated upwardly through its return stroke.

The number of inlet and exhaust channels 75 and 76, the angular lengths thereof, and the rotational velocity of the valve 69, are determined in accordance with particular tool designs and will depend upon a number of factors, such as the operating frequency of the tool and magnitude of the impact force or blow-striking energy desired. For a further discussion of a rotary valve of a type that may be used herein, reference may be made to my issued Patent No. 2,679,826.

The motor means 72 for driving the rotary valve 69 may be of any suitable type and, as indicated in FIG- URE l, m-ay be an air motorin which case, actuating air may be supplied thereto through a passage 79 communi-eating with the inlet passage 53 upstream of the manually controlled valve '7. In FIGURE 2, the motor means 72 is shown to -comprise a pair of electric motors supplied with electricity from a suitable source (not shown) that may be connected with the motors through `a plug or receptacle 80 conveniently provided along the outer casing structure of the tool, which casing structure is also seen to provide a compressed air inlet opening 53 adjacent the receptacle 80.

Returning to FIGURE 1, the chamber 54 is seen to connect directly with the inlet passage 53 upstream of the valve 57 and, therefore, is continuously supplied with pressure fluid whenever the tool is connected to a source thereof. Communicating with the chamber 54 is a hollow tube 81 that extends upwardly through the axially spaced flanges 23 and 21 provided by the sleeve 20. The upper end of the tube 81, which end is located within the constant pressure space 18d, is plugged or otherwise closed so that pressure fluid cannot flow therethrough; and the tube has formed therealong in spaced apart relation a pair of small apertures 82 and 83 respectively located within the constant pressure spaces 19d and 18d so as to supply pressure tiuid thereto. The apertures 82 and 83 are dimensioned so that a pressure drop occurs thereacross, and as a consequence thereof, the pressure within such constant pressure spaces is normally at a value substantially below the line pressure (i.e., at the inlet passage 53).

`Connected with the inlet passage 53 upstream of the valve 57 is a bore or passage 84 opening at its lower end into an inlet annulus formed in the circumferential surface of the ilange 37 which is integrally provided by the cylinder block 38. The annulus 85 (as seen best in FIG- URE 4) is connected by a passage 86 to a bore 87 from which pressure fluid is supplied to the constant pressure space 34 through a pressure regulator 88. The bore 87 is also connected to a tube 89' that extends downwardly therefrom through the constant pressure space 42d and into the constant pressure space 48d. The lower end of the tube 89 is plugged or otherwise closed, and the tube has formed therealong in spaced apart relation a pair of small apertures 90 and 91 that respectively communicate with the constant pressure spaces 42d and 48d and through which fluid is supplied to such spaces normally at a value reduced from the line pressure.

Returning again to FIGURE 4, it is seen that the flange 37 of the cylinder block 38 has a second channel or annulus 92 formed along the cylindrical surface thereof, which annulus is connected by a short passage 93 to an angularly oriented passage 94 formed in the outer casing 95 of the pressure regulator 88. The casing 95 defines therein a chamber or cylinder in which is mounted a helical spring 96 seating at its lower end upon the bottom end closure of the casing and seating at its upper end against the lower surface of a valve or piston element 97 reciprocable within the casing 95. A stop 98 extending upwardly from the bottom closure wall of the casing 95 positively limits downward displacement of the valve 97.

A ilow passage 99 is formed in the casing 95, and the How passage communicates at its lower end with the bore 87 and is adapted to communicate at its upper end with `an annulus 100 formed about the piston 97. The annulus 100 is connected by a flow passage 101 to the cylinder space above the piston element 97, and such cylinder space communicates through a port 102 in the top closure wall 103 of the casing 95 with the constant pressure space 34.

The exhaust annulus 92 communicates with atmosphere through a port in the outer casing element 12, as shown in FIGURE l; and, therefore, the lower surface of the piston element 97 is continuously main-tained at atmospheric pressure. Thus, the total force urging the piston element 97 upwardly comprises the atmospheric pressure force acting upwardly thereagainst and the resilient force of the spring 96.

Assuming the position of the pressure regulator shown in FIGURE 4, compressed air will ow from the inlet passage 53 and passage 84 into the annulus 85, passage 86 and bore 87; into the passage 99, annulus 100 and passage 101; and through the port 102 into the constant pressure space 34. The pressure in such space 34 will build up because of the continuous supply of pressure fluid thereto until the pressure reaches a value sutiicient to urge the piston element 97 downwardly to disestablish registration between the passage 99 and annulus 100.

Stich condition of non-registration will be maintained until the pressure within the constant pressure space 34 decreases in value to the extent that the piston element 97 will be displaced upwardly by the biasing force of the spring 96 to admit more pressure fluid to the constant pressure space and thereby build up the pressure therein to a greater value. This regulation continues automatically and as necessary to maintain the constant pressure space 34, and cylinder space 29 in communication there with, at a relatively uniform pressure value relative to the atmospheric pressure-generally, sufficient regulation is provided by such mechanism to maintain the space 34 and cylinder 29 at a relatively constant pressure value where the pressure uid being supplied to the coupling 51 is from a regulated source, which is usually the case.

The facing surfaces 14b and 15b respectively provided by the hammer 14 and oscillator 15 are arranged so as to absorb any impact force that develops therebetween as a consequence of impact-engagement of these two elements to prevent rebound or a bouncing action therebetween. In the form shown, such energy-absorbing means has two characteristics or factors. First, the surface 14h' has a concave, generally frusto-conical configuration and the surface 15b has a convex, generally frusto-conical configuration adapted to mate with the surface 14h. Secondly, the surface 15b is coated with an energy-absorbing substance having a low bounce or rebound factor, such as a silicone-rubber composition.

As a result of the first factor, compressed air disposed between the facing surfaces as the hammer and oscillator are displaced toward each other tends to be confined between the cone-shaped surfaces because it must be squeezed outwardly from therebetween through a progressively and incrementally decreasing flow space. Thus, such pocket of air between the cone surfaces defines a form of air cushion tending to prevent impact therebetween, but such pocket of air does not have the usual air cushion characteristic of causing bounce or rebound because the volume of air in such cushion progressively diminishes as the surfaces are moved closer and closer together. As a result of the second factor, any residual kinetic energy will be absorbed by the low-bou-nce energyabsorbing surface coating, and the hammer and oscillator will then remain in engagement with each other until separated by the admission of a charge of compressed air through the rotary valve 69. As will be brought out more fully hereinafter, the tool is operable so that the hammer 14 does not ordinarily engage the oscillator 15 after the valve 57 has been opened to initiate demolition operation of the tool.

In the percussive tool being considered, various area relationships are provided; and in this respect it will be evident that the axially projected areas of the hammer faces 14a' and 14b and of the oscillator faces 15a and 15b' are substantially equal. Although such area of the hammer facet14b is slightly less because of the presence of the grooves 14C, the total upwardly-facing pressurizable surface area on the hammer 14 necessarily includes the upper face of the hammer enlargement 14a which, therefore, has areas therealong respectively aligned with and corresponding in size to the grooves 14C, wherefore su-ch areas of the ham-mer enlargement 14a effectively form a part of the face 14h.

Also, the downwardly facing surface 28a of the cylinder end closure 28 is substantially equal in area to the axially projected area of the oscillator face 15a. The axially projected area of the downwardly facing surface 40a of the flange or piston 40C provided by the work member 41 is substantially equal to the area of the upwardly facing surface 39a of the work member. Accordingly, the area of the surface 39a is necessarily equal to the axially projected area of the upwardly-facing surface 43a' of the anvil-compensating cylinder 43, There fore, the sum of the axially projected areas of the surfaces 43a and 38a' is substantially equal to the downwardly facing surface 14a of the hammer 14 and, consequently, to the area of the surface 28a. Such surfaces 38a and 43a' may be ysometimes collectively referred to hereinafter as the lower reaction surface, and the surface, of the casing composition i, 28a as the upper counterbalancing surface, and in a somewhat similar sense, the pressurizable surface b of the oscillator 15 serves :as the upper reaction surface for the pressure fluid charge energizing the blow stroke of the hammer.

Quite evidently, the facing pairs of .surfaces respectively associated with the control cylinders 18, 19, 42 and 4S have substantially equal axially projected areas; and, therefore, the areas of the facing surfaces 18a and 18h are equal, as are the areas of the respectively facing surfaces 19a `and 19h, 42a and 42b, and 48a and 48h. The aggregate or composite cross sectional area of the exhaust portsassociated with the respective control cylinders is materially greater than the cross sectional area of the associated inlets; and in specific terms, Isuch area of the exhaust ports 13e materially exceeds the area of the associated automatic control inlet 83; and the corresponding relationship exists for the exhaust openings 19e and inlet 82, exhause openings 42e and inlet 89, and exhaust openings 48e and inlet 91. It will be noted that all of the exhaust port compositions 18e, 19e, 42e and 48e are of the same type and the purpose thereof, as has lbeen stated hereinbefore with particular reference to the port composition 18e, is to attenuate or dampen the corrective response of the automatic control systems so as to obviate or substantially reduce any tendency toward hunting action of the reciprocable components respectively traversing such port compositions.

The tool structure is assembled by inserting the plug 47, work member 41 and cylinder block 38 into the outer casing element 12 through the upper end thereof which is open when the cap 27 is removed. The sleeve 17 is mounted within the cylinder 13 of the inner casing element 11, and the head 15a of the oscillator is mounted thereon after the oscillator stem is inserted upwardly through the sleeve 17. The ring 36, rotary valve 69 and collar 20 are properly mounted upon -the inner casing 11; and with the hammer 14 within the cylinder 13, the inner casing is inserte-d into the outer casing element 12 through the open outer end thereof. Quite apparently, the tubes 81 and 89 are properly located, as well as the pressure regulator 88 and control valve assembly S7, prior to such mounting of the inner casing element 11 within the outer casing element 12.

With respect to the tubes 81 and S9, they .are respectively inserted into the openings provided therefor (the tube 81 being displaced downwardly through an opening shown by dotted lines in the upper sleeve flange 22, which opening is subsequently plugged) and are welded or otherwise fxedly and sealingly secured, as shown in FIGURE 1. With respect to the valve 57, the stern 58 thereof has a press fit -relation with the valve, or is otherwise fixedly anchored thereto after the stem has been displaced downwardly through the openings therefor in the various fianges of the sleeve 20, and the spring 59, and spring seat 60 will be properly located as the stern passes downwardly through the flange 21.

A recess in the handle T permits the rod 63 and cam 62 to be displaced outwardly to permit insertion of the inner casing element 11, sleeve 261, etc., into the outer casing element 12; and thereafter, the rod 63 is displaced inwardly into the operative position by a short pin that then remains within the handle, as shown in FIGURE l, to maintain such inward displacement thereof. The end closure 28 is then located upon the inner casing element, and the tube 2li inserted downwardly through the opening 28a in such plate and through the axially aligned bores in the oscillator 15 and hammer 14.

The cap 27 is then threaded onto the upper end of the outer casing element 12, and bears downwardly upon the end closure ZS-which places the inner easing element 11, cylinder block 3S and plug 47 in a state of compression because such serially related elements have a downwardly acting force applied thereto by the cap 27, and have an upwardly directed force applied thereto at the plug 47 by the bottom wall of the outer casing. As a result, the outer casing is in a state of tension and functions as a spring element holding the described parts in their assembled condition. Wherever appropriate, enlarged ports, annular chambers -and Aanalogous arrangements may be used to facilitate registration of the various interconnecting ports, passages and other air fiow spaces. Registration of the casing elements, sleeve 17, collar 20, ring 36, cylinder block 38, plug 47 and any other components may be determined and enforced in any convenient and conventional manner as, for example, by indexing or polarizig pins and recesses.

It is evident that a number of pressurizable ports, passages, cylinders and other chambers or spaces are defined between the circumjacent casing elements, collar Ztl), etc., and, therefore, a sealing relation must be established between such Components (at least in the vicinity of such pressurizable volumes) so 4as to precent leakage therefrom. The prevention of leakage may be accomplished in any suitable manner as, for example, by the inclusion of appropriate and conventional sealing elements or materials. In the specic structure being considered, the various contiguous surfaces where the occurrence of leakage is undesirable are finished to close tolerances, and may be coated with a thin layer of a suitable sealing or gasket compound (a conventional silicone-rubber gasket material, for example) prior to the assembly of the tool.

Positive air cushions are provided where necessary t prevent metal-to-metal impact, except as between the hammer 14 and work member 41 (and between the hammer and the oscillator as heretofore explained). Examples of provision for the establishment of su-ch air cushions are at the lower end of the cylinder 13 (where the inlet po-rts 35 are seen to be located a substantial distance above the cylinder end closure 38:1), and at the stationary surfaces associated with the various control cylinders 18, 19, 42 and 48. The motor means 72 and 72', shaft 71 and drive gear 70 are mounted upon the tool after the inner and outer casing elements and their associated components have been assembled.

As heretofore indicated, the axially projected area of the upwardly facing lower pressurizable surf-ace 43a' of the chamber 43 is substantially equal to the area of the upwardly facing, impact-.receiving surface 39a of the work member and evidently, then, the downwardly facing pressurizable surface at the lower end of the enlarged intermediate llange section 40C of the work member has substantially the same axially projected area -as that of the surface 43a and of the upwardly facing surface 39a'. Consequently, and because the lower end portion 29 of the cylinder 13 and lower end portion of the chamber 43 are connected to each other by passages 44, 45 and 46, such lower end portions of the cylinder 13 and chamber 43 are simultaneously pressurized, and the respective pressures therein are necessarily of substantially equal value. This relationship defines la compensated anvil, and the function and advantages thereof are described in detail in the aforementioned Patent No. 3,028,841, to which reference may be made for a complete description of this feature.

For convenience herein, however, it may be st-ated in general terms that a compensated anvil has the advantage of eliminating the waste of downpush momentum applied to the tool (and delivered through the spike or work member thereof to the concrete slab), which waste otherwise results from pressurization of the upwardly-facing, impact-receiving surface of the anvil between the intervals of impact of the hammer thereagainst. The downpush momentum wasted by pressurizing the anvil between the intervals of impact is obviated in the compensated anvil structure by pressurizing the downwardly facing surface 40a of the anvil or work member simultaneously with the pressu-rization of the upwardly facing impact-receiving surface 39a' thereof. These simultaneously applied equal-valued pressure forces acting downwardly upon and upwardly against the anvil-like upper end of the work member 41 substantially cancel each other since they are of equal value, and no net downward force, and therefore no downpush momentum, are then wastefully transmitted in this manner to the concrete slab.

In operation of the tool, pressurized fluid (usually compressed air as indicated hereinbefore) will be delivered to the inlet passage 53 (or 53'), and will llow downwardly therefrom into the composite volume defined by the lower end portion 29 of the main cylinder and constant pressure space 34 through the pressure regulator 88. Pressure lluid will also flow through the tube 89 and restricted inlet orices 90 and 91 into the constant pressure spaces 42d and 48d, and into the respectively associated control cylinders 42 and 48. Also, from the inlet passage 53, such pressure lluid will flow through the chamber 54, tube 31 and through the restricted orices 82 and 83 thereof into the constant pressure spaces 19d and 18d and into the respectively associated control cylinders 19 and 18. Evidently, pressure fluid will also be simultaneously supplied to the upper end portion 30 of the main cylinder and to the constant pressure space 32 in communication therewith through the axially extending tube 24.

The pressure forces continuously developed `within the control cylinders 13 and 19 will position the oscillator 15 substantially as shown-that is, certain of the outlet ports in each instance will be luncovered so that a continuous flow of a small volume of fluid will `move through such control cylinders and outwardly through the exhaust systems associated therewith. The illustrated position of the oscillator may be taken to be the normal mean position thereof which the control systems respectively comprising the `control cylinders 18 and 19 continuously attempt to enforce thereon. If the oscillator 15 ten-ds to be displaced upwardly from such mean position relative to the casing structure 10, a greater number of exhaust ports 18e will be uncovered permitting a larger volume of luid to escape from the cylinder 18, whereupon the pressure force therein acting upwardly against the surface 18h of the oscillator will diminish in value, thereby permitting the oscillator to be displaced downwardly toward its predetermined mean position. At the same time, such upward displacement of the oscillator 15 will close olf more of the exhaust ports 19e, thereby permitting a buildup of pressure iluid in the cylinder 19, whereupon the -resulting increased pressure force acting downwardly upon the surface 1% of the oscillator will displace it downwardly toward the predetermined mean position thereof.

In a completely analogous manner, the automatic control systems associated with the oscillatorl 15 function together but in a reverse manner when the oscillator is displaced downwardly from its normal mean posit-ion relative to the casing structure 10. In such instance, the exhaust ports 18e will `be closed to a greater extent and the exhaust ports 19e further opened or uncovered, whereupon the net pressure force acting upwardly against the oscillator 15 'will increase in value thereby returning the oscillator upwardly toward such mean position thereof.

The automatic control systems arranged with the work member 41 function in a substantially identical manner so that if the casing structure 10 is displaced downwardly relative to the work member (or the work` member is displaced upwardly relative to the casing), the exhaust ports 42e will be further covered by the piston 40a and the exhaust ports 43e will be further uncovered, whereupon the pressure within the control cylinder 42 will increase in value and that within the control cylinder 48 will decrease in value. As a result, the net upward pressure force then active upon the casing structure 10 will increase in value and displace the casing upwardly toward the mean position shown relative to the work member. On the other hand, if the work member 41 is displaced downwardly relative to the casing (or the casing is displaced upwardly relative thereto), the pressure within the cylinder 42 will decrease, that Within the cylinder 4S will increase, and the casing structure and Work member will then be returned toward their normal relative mean position.

This latter feature indicates that once the work member 41 is frictionally gripped by a concrete slab being penetrated thereby, the requirement for the tool operator to apply downpush or a feeding force to the tool is minimized -or obviated, because each time the work member 41 is displaced downwardly as a consequence of the impact force being delivered thereto by the hammer 14, the casing structure will be urged downwardly to reestablish the relative mean casing and work member position shown. Therefore, a feeding force is automatically provided at such time, thereby obviating the usual requirement for a manually applied feeding force.

The pressure simultaneously developed within the lower :and upper end portions 29 and 30 of the main cylinder will urge the hammer 14 upwardly and the oscillator 15 downwardly. However, in the case of the oscillator 15, such downward pressure force active upon the surface 15a' thereof will be opposed by the net upward pressure force active against the oscillator as a result of the operation of the automatic control -systems arranged with the control cylinders 18 and 19 which, as explained heretofore, tend to maintain the oscillator in a predetermined mean position. The hammer 14, hotwever, will be urged upwardly until it engages the oscillator 15, as shown in FIGURE l, which, then, may be taken to represent the normal condition of the tool prior to opening the valve 57 to initiate a demolition operation.

At the same time, the rotary valve 59 will be operating since the motor means 72 is being supplied with operating fluid through the passage 79 which is connected to the inlet passage 53. However, rotation of the valve 69 will have no influence on the condition of the tool because no pressure fluid is delivered to the rotary valve, until the main control valve 57 is opened. However, when the `operator depresses the lever 65 to open the -v-alve 57, pressure fluid flows into the manifold chamber 67 and passage 68; and when an inlet channel 75 establishes communication between the passage y68 and port 75', a charge of pressure iiuid lwill iiow into the annular chamber 16, through the grooves 14C and will act downwardly upon the upper surface 14b of the hammer. As a consequence, the hammer will `be driven downwardly toward impact-engagement with the upper surface 39a of the work member 41. Such charge of pressure fluid will be reactively applied against the surface 15b of the oscillator, thereby tending to reciprocate the same upwardly toward the end closure 28 of the cylinder 13.

As the rotary valve 69 continues to rotate, an outlet channel 76 thereof will move into registration with the port 75 which then will exhaust the cylinder space defined between the hammer 14 and oscillator 15. At the same time, the passage 68 will be closed by the upper surface of the rotary valve 69 to prevent the admission of more pressure fluid into the chamber 16. The hammer 14 will then be reciprocated upwardly by the pressure within the cylinder end 29 acting upwardly against the lower surface 14a of the hammer to return it to its uppermost position. In a similar manner, the oscillator 15 will be urged downwardly by the pressure fluid within the cylinder end portion 30 which acts against the upper surface 15a of the oscillator. This cyclic operation in which the hammer 14 is accelerated downwardly toward impact with the work member 41, and is subsequently accelerated upwardly through its return stroke, then continues for as long as the main valve 57 is open and the rotary valve 69 is operative.

Substantially no vibration is transmitted to the casing structure in consequence of the reciprocatory movements of thehammer 14 relative to the casing structure because the upwardly facing lower reaction surface comprising the axially projected areas of the surfaces 38a and 43a is substantially equal to the corresponding area of the upper counterbalancing surface 28a', and because such reaction and counterbalancing surfaces are continuously pressurized by pressures of substantially equal value. Therefore, no uncounterbalanced pressure force is applied to the casing structure by the pressure forces simultaneously developed within the cylinder ends 29 and 30, which force in the cylinder end 29 energizes the return stroke of the hammer 14. When the downstroke of the hammer is energized, the pressure uid admitted into the space between the hammer 14 and oscillator 15 and which accelerates the hammer downwardly is reactively applied against the oscillator 15 which is freely reciprocable with respect to the casing structure (it being recalled that the pressures within the spaces 18 and 19 remain substantially constant during cyclic reciprocation of the oscillator and do not, then, effectively resist such reciprocation thereof). Therefore,

no uncounterbalanced pressure force is applied to the casing structure in direct consequence of energization of the power stroke of the hammer.

As brought out in detail in the aforementioned Patent No. 3,028,841, the reciprocatory displacements of the hammer and oscillator generally do not have a same-phase (or an opposite-phase) relationship. Actually, the oscillator 15 at certain times may be moving upwardly during periods when the hammer 14 is being displaced upwardly, the oscillator and hammer may move downwardly together at certain times, and sometimes they may move in opposite directions. Accordingly, the relative volumes of the cylinder end portions 29 and30 are quite likely changing, and at certain times the volume of the space 29 and that of the space 30 may be decreasing concurrently. For the reasons heretofore set forth concerning the relationships of the lower reaction surface 38a-43a', the upper counterbalancing surface 28a', and the concurrent pressurization thereof with substantially samevalue pressures because of the effective flow communication linking such surfaces through the tube 24 (and passages 44, 45 and 46), any such changes in volumes as between the cylinder spaces 29 and 30 will not introduce vibration into the casing of the tool structure.

Reciprocatory displacements of the oscillator 15 relative to the casing structure 10 do not cause the casing structure to vibrate because of the constant-force relationships dened by the control cylinders 18 and 19 and their respectively associated constant pressure spaces 18a' and 19d during any one reciprocatory displacement of the oscillator, as explained previously. The same type of constant-force relationships are maintained by the control cylinders 42 and 48 and their respectively associated constant pressure spaces 42d and 48d, whereby displacements of either the work member 41 or casing structure with respect to the other do not cause vibration in the casing structure.

The oscillator 15 reciprocates through a range of movement having a normal mean position approximating that shown in FIGURE 1. If the mean position of such range of reciprocation has been displaced either upwardly or downwardly over a substantial number of reciprocations of the oscillator, the automatic control systems associated with the control cylinders 18 and 19 regulatively adjust the pressure forces therein so as to return the mean position of such range of reciprocation to its prior location. Thus, the automatic control systems associated with the oscillator, which systems function simultaneously and conjointly, continuously maintain the oscillator 15 in a condition of impact-preventing separation with the surfaces 18a and 19a of the sleeve 17 by maintaining the oscillator in such normal mean position thereof.

It is apparent that the intermittently supplied charges of pressure fluid admitted into the space between the hammer and oscillator must be superior in value to the pressure force acting upwardly upon the hammer 14 and downwardly upon the oscillator 15 in order that the reciprocatory cycle of the hammer lbe energized. The only requirement in this respect is that the differential in the fluid pressures be sufficient to energize the hammer 14; and that the differential be sufficiently great in magnitude that significant work may be done by the tool-that is, substantial impact energy should be delivered to the work member 41 by the hammer 14. By way of example, it is customary for the line pressure to be in the order of p.s.i. and the pressure within the cylinder spaces 29 and 3i) may 20 to 40 p.s.i.

In this respect, the presence of the tank spaces 34 and 32, which as explained heretofore are not required for elimination of vibration, assure maintenance of a substantial pressure ditferential as between the value of the continuous pressure within the cylinder space 29 acting upwardly against the undersurface 14a' of the hammer-and the intermittently applied pressure charges acting downwardly upon the hammer to energize the impact-delivering. MQW-@ OK@ @11.61 @Q More particularly, and by way of example, assume that the hammer 14 is descending toward the work member and `at the same time that the oscillator 1S is rising. When this condition prevails, both the cylinder space 29 and cylinder space 3ft are decreasing in volume w-hich usually is accompanied by an increase in pressure.

Should the decreased volume defined by the cylinder spaces 29 and 3th be so small as to cause the mean pressure under the hammer to approach line pressure (i.e., the pressure acting downwardly upon the hammer), no substantial impact would be delivered `by the hammer to the work member and no significant work would be done by the tool. The presence of the tanl: spaces 34 and 32 in respective communication with the cylinder spaces 29 and 30 assures a volumetric capacity ample to avoid such undesirable pressure rise below the hammer.

The hammer 1d `may be controlled and energized so as to have one or the other of two general types of operation. In the first type of operation, the hammer does not engage the oscillator l5 after initial separation therefrom upon actuation of the tool (that is, opening the main valve 57) and in the second type of operation, the hammer does engage the oscillator l5 during each cycle of reciprocation. In either type of operation, the ha-mmer 14 will be reciprocated downwardly when the rotary valve 69 admits a charge of pressure fluid through the port 75'; and assuming for convenience that such initial communication occurs at the originating end of a channel 75 so that a corn-plete charge of pressure fluid will be so admitted, the hammer will be driven into impact-engagement with the work member lll.

If the length of the exhaust channel '76 is made suciently short, if the value of the pressure within the cylin- -der space 29 is appropriately selected, and assuming the motor means 72 to be operating at a constant velocity, the hammer 14 can be controlled so that it does not have sufficient time during the backstroke or return stroke thereof to be reciprocated upwardly and into engagement with the lower surface 15b of the oscillator before the next charge of pressure fluid is admitted through the port 75 to energize the next blow-stroke of the hammer. Therefore, the next successive charge of pressure uid will commence to accelerate the hammer downwardly and into impact with the upper surface of the work member before the hammer engages the oscillator. Evidently, each such subsequent downward reciprocation of the hammer is through a slightly lesser distance than the initial downward reciprocation thereof and, therefore, the impact momentum of the hammer will be slightly less than on the initial blow stroke.

In an analogous manner, the variables may be selected and controlled to cause the hammer to engage the oscillator during each cyclic reciprocation of the hammer; i.e., on each lbaclcstroke thereof. ln this condition of operation, the hammer and oscillator will be in the engaged condition thereof when a charge of pressure fluid is admitted through the port 75. Therefore, the magnitude of the hammer blow, or the blow-striking energy contained by the `hammer at the instant of impact thereof with the work member will be greater than in the prior described cycle of operation because the stroke of the hammer will be of greater length and also because the hammer will contain some of the oscillator energy which was derived therefrom by such engagement of the hammer' therewith.

However, and as indicated hereinbefore, the cylinder spaces 29 and 30 are continuously pressurized whenever the tool is connected to a source of pressure fiuid. Accordingly, the hammer M and oscillator 15 are continuously biased toward each other and toward the condition of engagement illustrated in FlGURE 1 because of the pressure present in the cylinder spaces 29 and 39 (and their associated tank spaces 34 and 32, and a portion of the space 43 in the case of the cylinder space 29) which respectively act upwardly against the undersurface 14a' of the hammer and downwardly upon the surface 15a of the oscillator. Such pressure force-s tend to unify or integrate the hammer and oscillator components which are serially oriented within the main cylinder of the tool and define a binary mass selectively separable into the two com-ponents thereof upon the admission of a charge of pressure fluid between the two components which accelerates the hammer 14 Idownwardly toward impact-engagement with the Work member.

With respect to the specific tool under consideration, any feeding force applied to the too-l casing (which feeding force normally includes a manual `component applied to the handles of the tool) is transmitted through the casing to the oscillator 15 rathter than more directly to the reciprocable hammer, as is the case in the usual percussive tool structure. rThe path of the feeding force is through the outer and inner casing structures and through the variable-length linkage systems comprising the space i9.

The work member 41 shown, being of specially large diameter, has a greater life expectancy than the usual slender spike because it is less subject to fatigue, especially where the impact forces delivered thereto are of large magnitude. Further, such spike is a relatively heavy member of substantial mass and is operable to transmit heavy blows without substantial dirnunition thereof to a material to be demolished. The work member, as explained, is related to the casing structure through a pair of vibration-isolating linkages, and air cushions are defined within the extremities of the control cylinders 42 and 48 which prevent metal-to-metal impact of the Work member with the casing structure.

The percusive tool being considered may be referred to properly as a quadripartite structure comprising a casing composition, an oscillator, a hammer, and a work member. The oscillator and work member are each relater to the casing composition Eby a pair of force-transmitting linkages each of which comprises a constant force system and an automatic positional control system, wherefore there are a total of four such linkage systems in the tool structure. Thus, substantially no vibrationtrans-mitting force of either pneumatic pressure or impact origin is developed between the oscillator 15 and casing composition or between the work member 41 and casing composition. The hammer 14 reciprocates between the oscillator l5 and work member and is axially forcecoupled-conneoted to the casing composition only through the surface 38a of the casing the axial force transmitted therethrough being fully counterbalanced as described hereinbefore.

While in the foregoing specification embodiments of the invention have been described in considerable detail for purposes of making a com-plete disclosure thereof, it will be apparent to those skilled in the art. that numerous changes may be made in those details without departing from the principles or spirit of the invention.

I claim:

l. in combination, a plurality of mass members supported for relative reciprocation along a predetermined axis, one of said mass members being; an element in which the occurrence of vibration is undersirable and another thereof being a vibratory member, each other of said mass members being disposed along such axis in an axially force-coupled relation with said vibratory member effectively force-isolating the same in at least one of the directions of reciprocation thereof from said element, and each of said other mass members in respective association with said element defining a pair of relatively reciprocable opposed portions required to have a substantially continuous condition of impact-preventing separation therebetween during proper operation of the combination, and for each such pair of relatively reciprocabl-e opposed portions provided by said element and each other of said mass members: means defining a pressurizable enclosure and means for establishing therewithin a gaseous column extending between the associated opposed portions and transmitting a force therebetween, the volume of each said enclosure being so related to the increases and decreases in the volume of the associated column produced by each relative reciprocation of the associated opposed portions that substantially no change in pressure occurs within each said enclosure because of any such reciprocation, and means for automatically of adjusting the pressure within each said enclosure over a number of reciprocations of the associated opposed portions so as to maintain the said required condition of separation therebetween.

Z. The combination of claim 1 in which said last mentioned means comprises means yfor supplying 'gas under pressure to ea-ch said enclosure, means for permitting the escape of gas from each said enclosure, and means for regulating the relative rates of such escape and supply of gas so as to selectively increase or decrease the pressure therein so as to maintain the said required condition 4of separation.

3. The combination of claim 2 in which each said pressurizable enclosure -is provided with an inlet adapted to lcommunicate with a source of gas under pressure and with an exhaust outlet, and in which said means for regulating the relative rates or the escape and supply of gas includes a piston member carried by one of the associated relatively reciprocable mass members to traverse said outlet and maintain a selectively varia-bile control over the rate of exhaust flow therethrough.

4. In combination in a percussive tool having a vibratory element capable of simultaneously displaying both cyclic and random reciprocations and a casing element in which the occurrence of vibrationis undesirable, said casing element being provided with a main cylinder having a hammer-piston and also said vibratory element reciprocable in axial sequence therein, means dening a pair of conjointly-acting connecting linkages for effectuating a necessary transmission of force between said elements and each'said linkage dening a component of said force, each of said linkages including means dening a pressurizable enclosure and means for establishing therewithin a gaseous column extending between said elements and transmitting a force therebetween, the Volume of each said enclosure being so related to the cyclic increases and decreases in the volume of the associated column produced by the cyclic reciprocations of said vibratory element that substantially no change in pressure occurs within each said enclosure because of such cyclic reciprocations of the vibratory element, and means for automatically adjusting the pressure within each said enclosure in relation to the random reciprocations of said vibratory element for varying the value of each such force cornponent to maintain a predetermined operational relation between said elements.

5. In combination, a casing defining .a cylinder having a pair of serially disposed free-piston mass members reciprocable therein, one of said mass members being a hammer adapted to deliver repetitive impact force to a work member and the other thereof serving as a relatively heavy -oscillatory mass member to receive the reaction forces associated with energization of the blow-stroke of said hammer, means defining gaseous connecting linkage for eiiectuating a necessary transmission of force between said oscillatory mass member and said casing, means for automatically adjusting the value of such transmitted force to maintain a predetermined relation between said casing and oscillatory mass member, means for maintaining any such adjusted Value relatively constant throughout any cycle of the reciprocatory motion of said -oscillatory mass member, means for developing a gaseous pressure force between said mass members to energize the blow-stroke of said hammer and reciprocate the same free from said oscillatory mass member and toward impact `with said work member, and means for returning said hammer toward said oscillatory mass member following each such blow-stroke.

6. The combination of claim 5 in whch said oscillatory mass member and hammer are in substantial engagement prior to each such blow-stroke although otherwise structurally independent of each other.

7. In combination, a plurality of mass members relatively reciprocable along a predetermined axis, one of said mass members being an element in which the occurrence of vibration is undesirable, another thereof being a vibratory member, and at least one other mass member being disposed along such axis in an axially force-coupled relation with said vibratory member and force-isolating the same in at least one of the directions of reciprocation thereof from said element, means delining connecting linkage for eifectuating necessary :axial force transmission between said element and said other mass member, means for automatically increasing and decreasing componential values of such axial force to maintain a predetermined relation between said element and said other mass member, means for maintaining any such adjusted value relatively constant throughout any cycle of the vibratory motion of said vibratory member, any such adjustable component thereof being operative between relatively reciprocable opposed portions respectively defined by said element and other mass member, said predetermined relation including the condition of normally continuous irnpact-preventing separation between said element and said other mass member whereby the transmission of vibration to said element by repetitive stop-and-rebound action therebetween is prevented, and said connecting linkage comprising a gaseous medium interposed between said oppose-d portions.

8. The combination of `claim 7 in which said means for automatically increasing and decreasing componential values of such axial force comprises control means for automatically varying the pressure in said gaseous medium in response to changes in the positional relation of said element and said other mass member.

9. The combination of claim 7 in which said componential values together constitute such axial force.

it). In combination, a plurality of mass members relatively reciprocable along a predetermined axis, one of said mass members being an element in which the occurrence of vibration is undesirable and another thereof being a vibratory member, certain other of said mass members being respectively disposed along such axis in an axially force-coupled relation with said vibratory member and force-isolating the same in at least one of the directions of reciprocation thereof from said element, means defining connecting linkage for effectuating necessary axial force transmission between said element and said certain other mass members, meansfor automatically increasing and decreasing componential values of such axial force to maintain a predetermined relation between said element and said certain mass members, means for maintaining any such adjusted value relatively constant throughout any cycle of the vibratory motion of said vibratory member, any such adjustable component thereof being operative between relatively reciprocable opposed portions respectively deiined by said element and one of such certain other mass members, said predetermined relation including the condition of normally continuous impact-preventing separation between said element and at least one of said certain mass members whereby the transmission ot vibration to said element by repetitive stop-and-rebound action therebetween is prevented, and said connecting linkage comprising a gaseous medium interposed between said opposed portions.

lll. The combination of claim it) in which said certain other mass members are oriented so that at least one thereof is disposed in axially facing relation with said vibratory member along one side thereof and another is disposed in axially facing relation with said vibratory member along the other side thereof so that the vibratory member is force-isolated from said element in each axial direction.

12. The combination of claim 11 Comprising a percussive tool in which said element in which the occurrence of vibration is undesirable is a casing element, in which said vibratory member is a hammer, in which said one other mass member is a vibration-reducing oscillator, and said other mass member is a work member adapted to have repetitive impact force delivered thereto from said hammer.

13. The combination of claim 12 in which said casing element is provided with an axially extending cylinder in which said hammer and oscillator are reciprocable in axial sequence.

14. The combination of claim 13 in which said hammer and oscillator are in open and direct communication through said cylinder adjacent their facing end portions, said oscillator serving to receive the reaction forces associated with energization of the blow-stroke of said hammer toward impact delivery with said work member.

15. In combination, a plurality of mass members relatively reciprocable along a predetermined axis, one of said mass members being an element in which the occurrence of vibration is undesirable and another thereof being a vibratory member, certain other of said mass members being respectively disposed along such axis in an axially force-coupled relation with said vibratory member and forceisolating the same in at least one of the directions of reciprocation thereof from said element, means defining variable-length linkages respectively connecting said certain other mass members with said element for eifectuating axial force transmission therebetween, means associated with each said linkage for automatically increasing and decreasing the value of the axial force component defined thereby to maintain a predetermined relation between said element and each of said certain mass members, means for maintaining any such adjusted value relatively constant throughout any cycle of the vibratory motion of said vibratory member, each such adjustable force component being operative between a pair of relatively reciprocable opposed surface portions respectively defined by said element and by one of such certain other mass members, said predetermined relation including the condition of normally continuous impact-preventing separation between said element and each of said certain mass members whereby the transmission of vibration to said element by repetitive stop-andrebound action therebetween is prevented, and each of said linkages comprising a gaseous medium interposed between each such pair of opposed surface portions.

16. The combination of claim 15 in which said certain other mass members are oriented so that at least one thereof is disposed in axially facing relation with said vibratory member along one side thereof and another is disposed in axially facing relation with said vibratory member along the other side thereof so that the vibratory member is force-isolated from said element in each axial direction.

17. The combination of claim 16 comprising a percussive tool in which said element in which the occur rence of vibration is undesirable is a casing element, in which said vibratory member is a hammer, in which said one other mass member is a vibration-reducing oscillator, and said other mass member is a work member adapted to have repetitive impact force delivered thereto from said hammer.

18. The combination of claim 17 in which said casing element is provided with an axially extending cylinder in which said hammer and oscillator are reciprocable in axial sequence.

19. The combination of claim 18 in which said hammer and oscillator are in open and direct communication through said Cylinder adjacent their facing end portions, said oscillator serving to receive the reaction forces associated with energization of the blow-stroke of said hammer toward impact delivery with said work member.

20. In a percussive tool having a casing element in which the occurrence 0f vibration is undesirable and which casing is provided with a main cylinder having a hammer-piston reciprocable therein to effect the intermittent delivery of impact force to a `work member, a vibratory element axially reciprocable within said main cylinder, means dening a pair of conjointly-acting connecting linkages for effectuating a necessary transmission between said casing and vibratory elements of a force comprising co-linearly and oppositely active components, means for automatically adjusting the value of at least one such force component to maintain a predetermined operational relation between said elements, and means for maintaining any such adjusted value relatively constant throughout any cycle of the vibratory motion of said vibratory element, said means for automatically adjusting the value of each such force component including a pair of control means in respective association with said linkages for simultaneously adjusting the Values of the aforesaid components of such force to increase the value 0f one while decreasing the value of the other, and vice versa.

21. The percussive tool of claim 20 in which means are provided in respective association with each of said linkages for simultaneously adjusting the values of the aforesaid components of such force in opposite directions to increase the value of one while decreasing the value of the other and vice versa.

22. In a percussive tool composition, :a casing element providing a main cylinder and in which the occurrence of vibration is undesirable, a binary free-piston system axially reciprocable in said cylinder and comprising a pair of free-piston components disposed in axial sequence therein, means operative free of direct transmission of substantial uncounterbalanced axial reaction forces: to such casing element whereby such free-piston components can be subjected to axial forces relatively accelerating the same toward a condition of less distant axial separation there between, means operative free of direct transmission of substantial uncounterbalanced axial reaction forces to such casing element whereby such free-piston components can be subjected to axial forces relatively accelerating the same toward a condition of more distant axial separation therebetween, such tool composition including means effective to accomplish the impact deceleration of the reciprocatory motion in one axial direction of at least one such free-piston component, means effective for the useful delivery of the high-valued forces produced in such impact deceleration thereof to a work object, and con stant-force linkage means effective to transmit from such casing element to such binary free-piston system a unidirectional axial feeding force remaining of substantially invariant total value throughout each impact-developing operational cycle and urging such binary piston system in the direction of such high-valued force delivery to the work object.

23. The percussive tool -of claim 22 in which said constant-force linkage delivers said feeding force directly to at least one of the free-piston components of the binary free-piston system maintained thereby in an effective axial operational range.

24. The percussive tool of claim 23 in. which said constant-force linkage delivers .said feeding force directly to only one of such free-piston components.

25. The percussive tool of claim 24 in which said one free-piston component directly receiving the delivery of feeding force is the component other than that which is subjected to impact deceleration to develop the highvalued forces applied to the work object.

26. The percussive tool of claim 22 and further comprising an automatic positional control system operative upon said invariant total axial feeding force to selectively increase the value thereof during intervals comprising sub` stantial pluralities of such impact-developing operational cycles and decrease the value thereof during other such intervals as may be necessary to normally co-nne the axial operational range of such binary free-piston system within limits obviating the possibility of impact transmission of vibration from moving mass in such system to said casing element.

27. The percussive too-l of claim 22 in which said means accelerating the free-piston components into closer proximity, said means accelerating the same into greater 10 separation therebetween, and said constant-force linkage means are, respectively, uid pressure means.

241s References Cited by the Examiner UNITED STATES PATENTS FRED C. MATTERN, JR., Primary Examiner'.

BROUGHTON G. DURHAM, Examiner.

L. P. KESSLER, Assistant Examiner. 

20. IN A PERCUSSIVE TOOL HAVING A CASING ELEMENT IN WHICH THE OCCURRENCE OF VIBRATION IS UNDESIRABLE AND WHICH CASING IS PROVIDED WITH A MAIN CYLINDER HAVING A HAMMER-PISTON RECIPROCABLE THEREIN TO EFFECT THE INTERMITTENT DELIVERY OF IMPACT FORCE TO A WORK MEMBER, A VIBRATORY ELEMENT AXIALLY RECIPROCABLE WITHIN SAID MAIN CYLINDER, MEANS DEFINING A PAIR OF CONJOINTLY-ACTING CONNECTING LINKAGES FOR EFFECTUATING A NECESSARY TRANSMISSION BETWEEN SAID CASING AND VIBRATORY ELEMENTS OF A FORCE COMPRISING CO-LINEARLY AND OPPOSITELY ACTIVE COMPONENTS, MEANS FOR AUTOMATICALLY ADJUSTING THE VALUE OF AT LEAST ONE SUCH FORCE COMPONENT TO MAINTAIN A PREDETERMINED OPERATIONAL RELATION BETWEEN SAID ELEMENTS, AND MEANS FOR MAINTAINING ANY SUCH ADJUSTED VALUE RELATIVELY CONSTANT 